Black Locust
Robinia pseudoacacia L.

Black Locust: Full Size

Also known as Yellow Locust.

Mature Size: 30 to 70 feet tall and 1 to 2 feet in diameter.

Form: Medium-sized, with crooked branches; may form thickets through root suckering.

Habitat: Variety of sites, including disturbed areas; grows best on moist loams of limestone origin.

Leaves

Black Locust: Leaves

Alternate, pinnately compound, 8 to14 inches long, with 7 to 19 oval, smooth-edged leaflets.

Flowers

Black Locust: Flower

Showy and fragrant, white, 1 inch long and pea-like, borne in 5 inch hanging clusters, appearing mid to late spring.

Fruit

Black Locust: Fruit

2 to 4 inch, flat, brown pods containing 4 to 8 kidney-shaped, smooth, red- brown seeds, ripening in fall.

Bark

Gray or light brown, thick and fibrous, heavily ridged and furrowed, resembling a woven rope.

Twigs

Zigzag, somewhat thick and angular, red-brown with lighter pores; paired spines at each leaf scar (often absent on older or slow growing twigs); buds sunken beneath the leaf scars.

Values and Uses

The wood is yellow, coarse-grained, very heavy, very hard, strong and very resistant to decay. In the past it was used extensively for fence posts, poles, mine timbers, split rails and decking, as well as for pulpwood and fuel. Sprouts and seedlings are important food for cottontail rabbits and deer. Birds that eat black locust seeds include bobwhite quail and other game birds. Older trees with heart rot are used by cavity nesters, such as woodpeckers. The flowers are an important nectar source for honey production. Black locust is a nitrogen fixer and is good for reclaiming mine sites and other disturbed lands.

Did You Know?

Black locust is damaged by many insects and diseases, including locust borers, leafminers and heart rot fungi. Fungal growths are often present on the trunks.